Lung Volume Reduction Surgery Decreases Need for Oxygen Therapy

national emphysema treatment trial (NETT)--a large multicenter, randomized clinical trial of maximal medical therapy compared with LVRS for severe emphysema. During the trial, the researchers collected arterial blood gas data, performed a standardized oxygen titration test, and asked patients about supplemental oxygen use at baseline and at different time points after LVRS or medical therapy in patients with severe COPD.

The results showed that although the treatment groups were nearly identical at baseline, significantly larger percentages of medical patients had insufficient arterial blood oxygenation (PaO2) of 55 mm Hg or less at each follow-up visit, compared with LVRS patients (22% versus 10% at six months; 22% versus 14% at 12 months; and 25% versus 15% at 24 months). Significantly more LVRS patients than medical patients had a PaO2 at 24 months that was improved or stable compared with baseline (65% versus 39%).

Twenty-four months after randomization, 53% of LVRS patients with PaO2 of 55 mm Hg or less at baseline showed an increase to a PaO2 of greater than 55 mm Hg compared with only 17% in the medical group. Furthermore, while fewer medical patients required oxygen for treadmill walking at baseline compared with surgical patients (46% versus 53%), more medical patients required oxygen for treadmill walking at six months (49% versus 33%), 12 months (50% versus 36%), and 24 months (52% versus 42%). The study was published in the August 15, 2008, issue of the American Journal of Respiratory and Critical Care Medicine.

"LVRS as performed in the NETT results in an improvement in oxygenation that is small but significant,” said lead author Joshua Benditt, M.D.; however, he added, "no factor predicting a shift from needing oxygen preoperatively to not needing oxygen postoperatively could be identified.”

In LVRS, 20-30% of the diseased portions of the lungs are removed so that there is more room for healthy lung tissue to expand and carry on gas exchange, as well as more space for the diaphragm to take on its normal shape and function. Since normally there is a vacuum between the ribs and the lungs (which helps the lungs expand and fill with air when the chest wall expands), the main complication of LVRS is an air leak, which causes the lungs to sag. Therefore, the staples used during surgery are reinforced with a bovine cardiac membrane to prevent these leaks, much like adding bias tape to cloth to prevent tearing while sewing.

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